Metal oxide semiconductor (MOS) transistors having reduced channel lengths may suffer from parasitic short-channel effects. These effects can result in an effective reduction in transistor threshold voltage. One technique for reducing short-channel effects includes increasing the doping concentration in the channel region of the transistor. Unfortunately, this higher doping concentration may result in a higher inversion-layer channel resistance when the transistor is disposed in a forward on-state mode of operation. This higher channel resistance may cause a reduction in the current driving ability of the transistor. Another technique to reduce short-channel effects includes forming transistors having three-dimensional channel regions. One method of forming a transistor with a three-dimensional channel region is disclosed in U.S. Pat. No. 6,689,650 to Gambino et al. In this method, a gate electrode is formed in a self-aligned manner to a channel region. Other methods are disclosed in U.S. Pat. No. 6,448,615 to Forbes et al. and U.S. Pat. Nos. 6,605,501 to Ang et al.
Notwithstanding these methods, complications may arise when forming complementary metal oxide semiconductor (CMOS) transistors in a semiconductor substrate. These complications may relate to the inability to obtain optimum device characteristics for both NMOS and PMOS transistors because of the fact that electron and hole mobilities in these transistors are different. In order to obtain improved device characteristics, unique processing conditions may be necessary for each of the types of MOS transistors (i.e., N-type and P-type MOS transistors). However, these unique processing conditions may be difficult to apply to conventional CMOS methods of forming channel regions having three-dimensional shapes (e.g., fin-shaped channel regions).